So you've picked out the perfect pair of headphones, but they sound a little flat and quiet coming from your computer's crappy built-in audio. Here's a little gadget (or set of gadgets) that will make those headphones sound much better.

What a DAC and Amp Do

When you play music from your computer or mobile device, it goes through a Digital-Analog Converter (DAC) and an amplifier. The DAC converts the audio from a digital signal to an analog one (obviously), and the amplifier is what sends it to your headphones. The problem is, most devices don't have very good DACs or amps built in. So, if you get a nice high-end pair of headphones, you may still be getting less than ideal sound from your computer or MP3 player. That's where an external DAC and amp come in. (If you're just using the default iPod headphones, turn back now. A DAC isn't going to help you at all.)

An amplifier boosts the volume of the sound, which is particularly useful for higher impedance headphones (headphones above 32Ω) that will sound quiet through a regular headphone jack.

Amplifiers will often come with other features, like bass boost or other equalizer functions, that allow you to alter the sound.

Note that you can only get the full benefit of a DAC/amp combo with your desktop or laptop computer, via USB or SPDIF. While you can get DAC/amp combos for iPods and other mobile devices, the DAC half of the device won't actually work. Only the amp half will. This is still great for giving your sound a boost in volume if it's coming out too quiet, but just know that the DAC won't work—so if you only plan on using it with an iPod, you don't need a DAC or combo, just a mobile amp.

Which DAC and Amp to Buy

You have a lot of different DACs and amps to choose from, with different features, inputs and outputs, and form factors. Here are a few different types you'll see:

Portable Amps: If you have a pair of high-impedance headphones that just won't get loud enough with your portable music player (like a smartphone), a portable amp—which doesn't usually contain a DAC at all—is ideal. The $25 Fiio E6 is a good example of this.

Desktop DACs: These can either be coupled with a desktop amp for your headphones, or used alone (usually if your computer produces interference with your build-in sound card). These can range from the budget-focused Behringer UCA202 ($30) to the more expensive Schitt Modi ($109) or the JDS Labs ODAC ($150).

Desktop Amps: If you don't need a DAC (or if you're pairing a separate DAC and Amp), a desktop amplifier will help boost the volume of your headphones. The FiiO E09k ($109) is a decent budget amp, but if you're willing to spend a little more, the Schitt Magni ($109) and JDS Labs O2 ($130) are also popular options (and a little more well-built).

DAC/Amplifier combos: If you want both a DAC and amp together in one package, you have quite a few choices. I like the Audioengine D2 ($169—buy it refurbished if you can), which works well with both headphones and speakers. If you're on more of a budget, the FiiO E10k ($75) is a popular choice. You can also get the ODAC and O2 combo unit from JDS Labs ($279). If you want something that can be used on-the-go, the $88 Fiio E17 is designed for both mobile devices and computers.

The above section has been updated since the publishing of this article for a more well-rounded selection of DACs and amps at different price points.

As you look through each of these, you'll find that they all have different outputs, feature sets, and so on. For example, some may have a bass boost knob, while others will automatically mute your speakers when you plug headphones in. These are far from the only options, too—you can see more suggestions in our DAC Hive Five.

A good digital-to-analog converter (or DAC) can make all the difference when listening to music,…
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You get the idea, though: which one you buys will depend on your headphones, the device you're using to play the audio, and your personal preferences. Before you buy, read reviews and check out forums like Head-Fi for more detailed information on each model, especially when pertaining to a specific set of headphones. I've also found the Audiophile subreddit over at Reddit to be full of especially helpful and honest people. As long as you do your research, you should end up with something that takes your headphones from good to great with little effort.

Do you have any experience with DACs and amps? Share your thoughts, findings, and other opinions in the comments below.